Graph- and ontology-augmented foundation models for biomedical knowledge discovery and clinical NLP

Abstract

Biomedical knowledge discovery and clinical natural language processing increasingly rely on foundation models, but these approaches face persistent challenges, including incomplete curated knowledge, instability in language model outputs, and ambiguity in clinical interpretation. This dissertation argues that reliable biomedical AI requires integrating structured knowledge and foundation models through complementary control mechanisms rather than relying on any single method. To support this argument, the dissertation presents a unified framework across molecular and clinical domains. It develops an iterative prompt refinement approach with retrieval-augmented generation to improve the reliability of biomedical relation extraction, introduces graph transformer models to infer gene–gene relations and augment incomplete pathway knowledge, and proposes ontology-grounded retrieval and normalization pipelines to improve semantic alignment in multidisciplinary clinical notes. Together, these contributions define a layered reliability framework in which graph-based inference addresses knowledge incompleteness, retrieval-augmented prompt control mitigates instability, and ontology grounding reduces semantic ambiguity, providing a foundation for more reliable biomedical AI systems.